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Three-Dimensional Hierarchical Flowerlike α-Fe2O3 Nanostructures: Synthesis and Ethanol-Sensing Properties
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Published: November 06, 2011
r
2011 American Chemical Society
4689 dx.doi.org/10.1021/am201112z
|
ACS Appl. Mater. Interfaces 2011, 3, 4689–4694
RESEARCH ARTICLE
www.acsami.org
Three-Dimensional Hierarchical Flowerlike α-Fe
2
O
3
Nanostructures:
Synthesis and Ethanol-Sensing Properties
LiLi Wang, Teng Fei,* Zheng Lou, and Tong Zhang*
State Key Laboratory on Integrated Optoelectronics, College of Electronic Science, Engineering, Jilin University, Changchun 130012,
People’s Republic of China
1. INTRODUCTION
With the advancement in materials science, hierarchical
structures materials open a new horizon for the investigation of
high-performance sensors, and are considered as good candi-
dates for gas sensors because of their low density and large
surface-area-to-volume ratio than solid structures.
14
To date,
many types of hierarchical superstructures have been successfully
fabricated by a variety of methods.
59
However, these methods
usually hold disadvantages related to high temperatures or
tedious synthetic procedures, which possibly result in the in-
creased cost and limited the potential applications. Therefore,
exploration of a simple, mild and economical approach is strongly
desirable for the fabrication of hierarchical nanostructures.
1015
Nevertheless, in spite of extensive research efforts, synthesis of
hierarchical structures by a simple solvothermal route still
remains a technological challenge.
Hematite (α-Fe
2
O
3
), an n-type semiconductor (E
g
= 2.1 eV), is
the most thermodynamically stable phase of iron oxide under
ambient conditions with low cost, high resistance to corrosion and
environment-friendly features. It has been extensively investigated
for various applications, such as catalysts, gas sensor, electronic
materials, magnetic devices, biological and medical fields.
1621
Stimulated by these intriguing properties and broad applications,
well-defined nanostructures of iron oxides with different dimen-
sionalities such as 0D (nanoparticles),
22
1D (nanorods, nanowires,
nanotubes,
23,24
2D/3D (nanorings, nanobelts, nanocubes, as well
as hollow and porous nanostructures)
25,26
have been successfully
obtained. Until now, the simple synthesis strategy for the flower-
like α-Fe
2
O
3
hierarchical structures is still rarely reported.
In this work, we report a simple strategy for the synthesis of
flowerlike α-Fe
2
O
3
hierarchical structures through a solvothermal
process with subsequent calcination of the obtained precursor.
The obtained α-Fe
2
O
3
hierarchical architectures consisted of a
number of two-dimensional (2D) nanosheets. The formation
mechanism as investigated in detail. A comparative gas sensing
study between the as-synthesized α-Fe
2
O
3
hierarchical architectures
and α-Fe
2
O
3
compact structures was performed to demonstrate the
excellent gas sensing properties of α-Fe
2
O
3
hierarchical materials.
2. EXPERIMENTAL SECTION
2.1. Materials. All the reagents were of analytical grade and
used without further purification. Ferric chloride (FeCl
3
3
6H
2
O),
urea, ethylene glycol and glycerol were purchased from Sino-
pharm Chemical Reagent Co. (Shanghai, China).
2.2. Synthesis Process. Flowerlike α-Fe
2
O
3
hierarchical
structures was prepared through a two-step process including
solvothermal synthesis of FeOOH precursor and calcination of
the obtained precursor. In a typical experiment, 0.15 g of
FeCl
3
3
6H
2
O and 0.2 g of urea we re mixed with 25 mL of
ethylene glycol under magnetic stirring vigorously until a uni-
form suspension was formed. The suspension was then trans-
ferred into a 40 mL teflon-lined stainless steel autoclave. After
sealing, the autoclave was heated at 160 °C for 8 h, and then
cooled naturally . The product was collected by centrifugation,
washed with deionized water and absolute ethanol several times ,
and finally dried in vacuum at 60 °C for 6 h. The dried powder of
the precursor was heated in air from room temperature to 500 °C
Received: August 18, 2011
Accepted: November 5, 2011
ABSTRACT: The α-Fe
2
O
3
hierarchical nanost ructures have
been successfully synthesized via a simple solvothermal method.
The as-prepared samples are loose and porous with flowerlike
structure, and the subunits are irregularly shaped nanosheets.
The morphology of the α-Fe
2
O
3
structures was observed to be
tunable as a function of reaction time. To demonstrate the
potential applications, we have fabricated a gas sensor from the
as-synthesized hierarchical α-Fe
2
O
3
and investigated it for
ethanol detection. Results show that the hierarchical α-Fe
2
O
3
sensor exhibits significantly improved sensor performances in
comparison with the compact α-Fe
2
O
3
structures. The en-
hancement of sensing properties is attributed to the unique
porous and well-aligned nanostructure.
KEYWORDS: α-Fe
2
O
3
, hierarchical structures, rapid response, gas sensor
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